Boiler units for energy production systems have been utilized for coal burning power plants and the like. Such boiler units utilize air and send air to a furnace to combust coal to create steam that is subsequently used for generating electricity. Boiler units utilized in electricity production and other components of such systems are described, for example, in U.S. Patent Application Publication Nos. 2012/0052450, 2012/0145052, 2010/0236500, and 2009/0133611 and U.S. Pat. Nos. 7,954,458 and 6,505,567.
Oxy-combustion is a development for carbon dioxide capture and sequestration in fossil fuel (e.g. coal, etc.) fired power plants to replace combustion air with a mixture of oxygen and recycled flue gas to create a high carbon dioxide content flue gas stream that can be more easily processed for usage (e.g. enhanced oil recovery) and/or sequestration. In U.S. Patent Application Publication No. 2012/0145052, it is disclosed that some oxy-combustion systems may include an air separation unit, a boiler, a pollution control system, and a gas processing unit for recycling flue gas. The heat from combustion and the residual heat in the flue gas of the boiler may be used produce superheated steam to drive a steam turbine generator to produce electricity. The flue gas may then be processed to remove certain pollutants (e.g. NOx, SOx, etc.) and a portion of the treated flue gas may then be recycled to the boiler to effect combustion. As disclosed in U.S. Patent Application Publication No. 2012/0134042, oxygen is added to the recycled flue gas based on how much fuel is to be combusted in the boiler. The oxygen is added to the flue gas to form a single oxidant flow and that single oxidant flow is then fed to the boiler. Such systems are susceptible to inefficiency and to system degradation.